This is tough. I would have hoped that he wouldn't cheat and just break up with his fiance first, but these are booty call hours. Its hard to figure out what you want in a person unless you're with someone. We can list qualities all we want but until we are actually with someone, we don't really know. I had all these ideas of who I wanted before I met my wife. Guess what that list went out the window and she had qualities that I didn't even know I wanted and needed. She was more different than anyone I had ever dated and it was completely accidental.
From chapter 1, I knew Kaori was wrong for Osu. The fact that 1, she would tell him to say that nonsense and 2, he would say it, told me that that relationship was screwed up. I've said this before but Osu was also affected by his parents relationship and divorce. He's just been going with the flow and doing what he thinks is right without any of his real feelings being into it. She's been calling the shots and he's been following. If there was no Hara sensei, they would probably get married and have a kid or two but the marriage would end in divorce with one or both leaving. Osu would eventually realize that he was never in love with Kaori and cheat. Or Kaori would realize that she doesn't want a man that's a pushover on everything and cheat on him. Even worse would be if she just cheated and stayed because she know he wouldn't leave her. Either way, the future is bleak in their relationship. Leaving her in the middle of the night is an absolute dick move though.
@First_Mate_Zoro what's this medical manga everyone's talking about and why focus on a manga that's stalled over one that's completed?